The degree of integration of integrated circuits has recently become much higher, and the processing of ultra-fine patterns having a line width of a quarter micron or below is required in the production of semiconductor substrate, for example, VSLI. In order to form fine patterns, means of reducing a wavelength of exposure light source for use in the production of resist patterns is known.
For instance, in the production of semiconductor device having the degree of integration up to 64 Mbits, an i-line (365 nm) of high pressure mercury lamp has been employed as the light source. As a positive resist corresponding to the light source, a large number of compositions containing a novolak resin and a naphthoquinone diazide compound as a photosensitive substance have been developed. These compositions have achieved full success in the processing of linewidth up to about 0.3 μm. Also, in the production of semiconductor device having the degree of integration of 256 Mbits or more, a KrF excimer laser beam (248 nm) is employed as the light source in place of the i-line.
In recent years, for the purpose of the production of semiconductor device having the degree of integration of 1 Gbit or more, as a light source having shorter wavelength, the use of an ArF excimer laser beam (193 nm) and further, the use of an F2 excimer laser beam (157 nm) in order to form a pattern of not more than 0.1 μm have been investigated.
In response to such a trend of using light source having a shorter wavelength, constituent components of the resist materials and structure of compounds used for the constituent components have been greatly changed.
As the resist composition for exposure using a KrF excimer laser beam, a composition in which a resin including a basic skeleton of poly (hydroxystyrene) that has a small absorption in the region of around 248 nm and being protected by an acid-decomposable group is used as the main component and a compound that generates an acid upon irradiation of a far ultraviolet ray (a photo-acid generator) is used in combination, that is, a so-called chemical amplification resist has been developed.
Further, as the resist composition for exposure using a ArF excimer laser beam (193 nm), a chemical amplification resist using a resin having an alicyclic structure, which do not have an absorption at 193 nm, introduced into the main chain or side chain has been developed.
It has been found in case of using an F2 excimer laser beam (157 nm), however, that since the above-described alicyclic group-containing resin still has a large absorption in the region of around 157 nm, it is insufficient for obtaining the desired pattern of not more than 0.1 μm. In the circumstances, it is reported that a resin having a fluorine atom (a perfluoro structure) introduced therein has sufficient transparency in the region of around 157 nm in Non-Patent Document 1 (Proc. SPIE., Vol. 3678, Page 13 (1999)). Also, the structures of effective fluorine resins are proposed, for example, in Non-Patent Document 2 (Proc. SPIE., Vol. 3999, page 330 (2000)), Non-Patent Document 3 (Proc. SPIE., Vol. 3999, page 357 (2000)), Non-Patent Document 4 (Proc. SPIE., Vol. 3999, page 365 (2000)), Patent Document 1 (WO 02/33489) and Patent Document 2 (WO 02/092651), and resist compositions including a fluorine-containing resin have been investigated.
However, in resist compositions for F2 excimer laser beam including a hitherto known fluorine-containing resin, it is necessary to increase a fluorine content in the resin in order to increase transparency. However, as the increase in the fluorine content in the resin, the resist film formed becomes water-repellent and as a result, development defect and scum (development residue) tend to occur.
Further, with respect to conventional resist compositions for F2 excimer laser beam, there is room for improvement in defocus latitude. Specifically, when the resolution of lithography comes close to the limit in accordance with the miniaturization of processing size of pattern, it is difficult to ensure sufficient defocus latitude. Thus, a resist having a broad defocus latitude has been desired. The term “resist having a broad defocus latitude” means a resist in which variation of linewidth based on the defocus is small.
Non-Patent Document 1: Proc. SPIE., Vol. 3678, Page 13 (1999)
Non-Patent Document 2: Proc. SPIE., Vol. 3999, page 330 (2000)
Non-Patent Document 3: Proc. SPIE., Vol. 3999, page 357 (2000)
Non-Patent Document 4: Proc. SPIE., Vol. 3999, page 365 (2000)
Patent Document 1: WO 02/33489
Patent Document 2: WO 02/92651